1. Field of the Invention
The present invention relates to a method for producing a ceramic electronic component, and more particularly, to a method for producing a ceramic electronic component, which includes a step of providing a component main body with water repellency in order to prevent the ingress of moisture into the ceramic electronic component.
2. Description of the Related Art
The ingress of moisture into a void section of a ceramic electronic component causes degradation of reliability, such as electrical insulation and lifetime characteristics. The ingress of moisture is likely to occur, for example, during a plating process which is performed to form external terminal electrodes and during use in a high-humidity environment. In particular, in a laminated ceramic electronic component including a component main body which has a laminated structure, the ingress of moisture is likely to occur through gaps at the interfaces between internal electrodes and ceramic layers. In this case, even when external terminal electrodes are formed on the outer surface of the component main body so as to be electrically connected to the internal electrodes, with the result that the interfaces between the internal electrodes and the ceramic layers are covered with the external electrodes, the ingress of moisture may be caused due to various voids and gaps. In particular, when the external terminal electrodes are formed only by plating, the ingress of moisture is more likely to occur.
As methods for preventing the ingress of moisture as described above, methods for providing a water repellent agent (which may be referred to as a “waterproof agent” in some cases) have been proposed.
For example, the techniques described in Japanese Patent No. 3304798 and Japanese Patent No. 3444291 are intended to prevent the ingress of moisture by forming a water repellent film on the surface of a ceramic body or on the surfaces of external electrodes before performing a plating process on the external electrodes. It is to be noted that, in Japanese Patent No. 3304798 and Japanese Patent No. 3444291, the water repellent film is formed by immersing the ceramic body with the external electrodes formed thereon in a water repellent agent under atmospheric pressure or under reduced pressure in a vacuum.
On the other hand, a technique described in Japanese Patent No. 4167360 is intended to prevent the ingress of moisture by performing a plating process onto external electrodes and then impregnating a porous section of the surface and inside of the external terminal electrodes with a water repellent member. In this case, a chip subjected to a plating process is immersed in the water repellent member under reduced pressure in a vacuum in the step of impregnating the porous section with the water repellent member. In addition, as described in Japanese Patent No. 4167360, the water repellent member is removed from the surface of the external terminal electrodes in order not to damage the appearance or the wettability.
As described above, the impregnation with the water repellent agent is performed under atmospheric pressure or under reduced pressure in a vacuum in the techniques described in Japanese Patent No. 3304798, Japanese Patent No. 3444291, and Japanese Patent No. 4167360. However, the simple impregnation under atmospheric pressure or under reduced pressure in a vacuum may fail to cause the water repellent agent to sufficiently penetrate deeply into minute voids, thereby resulting in an insufficient water repellent effect and, thus, degrade reliability.
In addition, as in the case of the techniques described in Japanese Patent No. 3304798 and Japanese Patent No. 3444291, when a step of removing the water repellent film is not performed after the formation of the water repellent film on the surface of the ceramic body and the surface of the external electrodes, the excessively high water repellent ability of the water repellent agent may cause problems such as defective film deposition or defective film adhesion in a subsequent plating process. However, conversely, when emphasis is placed on the prevention of the problem in the plating process and the water repellent agent used has a reduced water repellent ability reduced, the essential effect of preventing ingress of moisture will not be sufficiently produced. For these reasons, the techniques described in Japanese Patent No. 3304798 and Japanese Patent No. 3444291 are significantly limited in terms of the selection of the water repellent agent and the conditions for the impregnation.
On the other hand, when a step of removing the water repellent member is performed after the impregnation with the water repellent member as in the technique described in Japanese Patent No. 4167360, the insufficient removal may cause problems in terms of appearance and soldering properties, whereas the excessive removal will fail to provide the essential effect of preventing ingress of moisture sufficiently. For these reasons, the technique described in Japanese Patent No. 4167360 is also significantly limited in terms of the selection of the water repellent member and the conditions for the impregnation, and further significantly limited in terms of the conditions for the removal.